1. Field of the Invention
This invention relates to a method for inhibiting corrosion of iron-containing alloy articles, particularly tubular articles of, for example, carbon steel, in a sulfur-containing corrosive media, such as hydrogen sulfide.
2. Description of the Prior Art
In various applications, and particularly in deep gas and oil-well production and drilling applications, there is a need for material that is corrosion resistant, and particularly resistant to corrosion caused by sulfur-compound containing environments, such as those containing hydrogen sulfide. In deep-well production and drilling applications, commonly termed sour well applications, the drilling components, and particularly the tubing extending into the well, are subject to environments containing various levels of hydrogen sulfide, often in combination with carbon dioxide, brine, and various hydrocarbons. Tubing used for this purpose is for reasons of economy made from carbon steel. In the presence of hydrogen sulfide encountered in sour well applications, corrosion of the carbon steel occurs as a result of the iron reacting to form iron-sulfide phases, particularly on the inner wall surfaces of the tubing extending into the well and subjected to the sulfide environment.
More particularly, in sour gas environments, the iron-containing alloy, e.g. carbon steel, undergoes attack by sulfur-containing compounds such as hydrogen sulfide, resulting in the formation of a scale of various ferrous sulfide phases such as pyrite and marcasite (FeS.sub.2); pyrrhotite (Fe.sub.1-x S); and mackinawite, (Fe.sub.1+x S). In accordance with the present invention, it has been found that ferrous ions are rapidly transported through such sulfide phases, in particular the pyrrhotite phase, and react with the sulfur containing compound at the outer surface leading to the corrosion process.
More highly corrosion resistant materials add, if substituted for carbon steel, significantly to the overall cost of the extraction operation.